The present invention relates to a control method for a digital copier which is operable in a two-sided document copy mode using an automatic document feeder (ADF).
It is a common practice with a digital copier of the type described to effect a two-sided document copy mode by feeding a two-sided document while turning it over so as to read a second side (rear) of the document by a scanner, copying it a desired number of times, turning over the document by an ADF, reading a first side (front) of the document by a scanner, copying the first side the desired number of times, replacing the document with another two-sided document, and then repeating the above procedure with the new document. The problem with such a procedure is that in the two-sided document copy mode, the ADF has to turn over each document in the event of replacement, resulting in a lower continuous coping speed than in a one-sided document copy mode. Consequently, the operation efficiency of the entire copier is limited. In this respect, there has been proposed to read a document image by a scanner, write the resulting image data in a memory, and print out the image data repeatedly (so-called memory retention). This kind of scheme reduces the wasteful interval between the end of document reading and the beginning of the next document reading (e.g. a time necessary for the scanner to return), thereby reducing a repeat copying time. However, such an approach cannot deal with a two-sided document copy mode. Moreover, an interrupt function available with the conventional digital copier is not satisfactory since even when a person desires to use only the scanner, the entire copying operation has to be interrupted. This is troublesome in various aspects, e.g., the continuation of the remaining copying operation and the resetting of documents.